The ships were hit by Typhoon Wutip on Sunday as they navigated gales near the Paracel Islands, about 330 km from China's island province of Hainan, the agency said, citing sources with the Hainan maritime search and rescue centre.

Rescuers had rescued 14 survivors, the sources said. The boats were sailing from the southern province of Guangdong.

Rains from the storm are expected to reach Vietnam on Monday before hitting Thailand on Tuesday.

Thai officials warned that more heavy rains could inundate already flood-hit areas of the northeast. At least 22 people have been killed in this year's flooding.

"We're expecting more floods," Teerat Ratanasevi, a government spokesman, told reporters on Monday. "Soldiers have been asked to help evacuate people trapped in flood zones."

Authorities in central Vietnam have moved children and elderly people to schools and other more solid buildings ahead of the storm.

In the central province of Quang Tri, an estimated 82,000 people would need to be evacuated if Wutip made a direct hit, a government statement said.

Vietnam said heavy rain had been falling in several central provinces while flooding and landslides could strike the region later this week.

The region has been hit by a number of typhoons including typhoon Usagi which killed 20 people earlier this month and caused massive flooding.

Typhoons gather strength from warm sea water and tend to dissipate after making landfall. They frequently hit Taiwan, Japan, the Philippines, Hong Kong and southern China during a typhoon season that lasts from early summer to late autumn.